The primary purpose of this research is to investigate the mode of inheritance of genes involved with essential hypertension and with blood pressure regulation in general. By helping to define factors related to increased risk of essential hypertension, we may help account for differences in blood pressure among various subgroups of the population; provide a basis for a better understanding of the basic disease mechanism; and perhaps most importantly, provide a method that can be used to identify children that have a high risk of developig the disease. We have ascertained four very large multigeneration families (average 150 participants each) through men known to have essential hypertension. Family members are given an extensive physical exam and a battery of test including: anthropometric measures, biochemical measures (e.g., renin, kallikrein, aldosterone, DBH, lipoprotein, genetic markers), psychological tests, physiological tests (including non-invasive measures of systolic time intervals, etc. from ECG, phonocardiogram, carotid pulse, dP/dt, foot pulse, respiration, forearm blood flow, and blood pressure) in response to certain stresses (e.g., mental stress, cold pressor, faceimmersion, isometric exercise, tilt). These data will be analyzed using recently developed statistical methods designed for segregation and linkage analysis of quantitative traits.